Medical device electronics
Two things separate medical from ordinary industrial work: the isolation barrier has to be justified against a specific means of protection, and every decision has to be evidenced. A design you cannot defend on paper is a design you have not made.
Evidence
What we can substantiate
Everything below is work we have actually done, described at a level that respects the client’s confidentiality. If you need detail, ask under NDA.
- Isolation designed to a stated means of protection MOOP and MOPP are different barriers with different creepage, clearance and dielectric requirements, and 2× MOPP for a patient-connected part is a long way from what a general-purpose isolator gives you. We decide the classification first, then select isolators and optocouplers whose certified ratings actually cover it, and record the working voltage the calculation used.
- Leakage current budgeted, not measured and hoped Earth leakage, touch current and patient leakage each have their own limit in normal and single-fault condition. Y-capacitors across the barrier are usually what breaks the budget, and they are chosen for EMC by someone who is not tracking leakage. We reconcile the two rather than trading one failure for the other.
- IEC 60601-1-2 immunity, which is the harder half Medical EMC is not mainly about emissions. It is 10 V/m radiated immunity, ESD to 8 kV contact, surge and fast transients — with the requirement that the device either keeps working or fails safe and says so. That constrains watchdogs, input filtering, ADC front ends and the software's reaction to a corrupted reading.
- Single-fault condition analyzed at component level The standard asks what happens when any one component fails short or open. That is a design activity with a written output, not a review comment — and it frequently changes the topology, because a part whose failure is unacceptable needs a redundant partner or a different circuit.
- Design records built as you go Requirements traced to implementation, review packages with findings and dispositions, and rationale captured while it is still fresh. Assembling this after the fact costs several times what capturing it costs, and reviewers can tell the difference.
- Class 3 assembly and the cleanliness question decided early IPC-A-610 Class 3 workmanship, with the no-clean versus aqueous-clean decision made before layout — because it changes pad design, component spacing and whether conformal coating will adhere.
Common questions
Straight answers
What is the difference between MOOP and MOPP, and why does it cost money?
A means of operator protection assumes a healthy adult who can let go; a means of patient protection assumes someone connected to the device who cannot. MOPP therefore demands larger creepage and clearance and a higher dielectric test, and 2× MOPP roughly doubles it again. The commercial consequence is that a general-purpose digital isolator rated for basic reinforced insulation often does not carry the certification you need, and the parts that do are more expensive and larger. Deciding this before layout is the difference between a component change and a board respin.
We are not a medical company. Can you take us through 60601?
We can do the electronics design to the standard and produce the records that support it, and we work alongside your regulatory consultant or notified body. What we do not do is act as your regulatory authority — the risk management file, the clinical evaluation and the QMS are yours. Where you have none of that yet, say so early and we will tell you honestly what has to exist before the electronics work is worth starting.
Why is immunity harder than emissions for medical devices?
Because the acceptance criterion is behavioral, not numeric. An industrial product passes emissions by staying under a line. A medical device has to demonstrate that at 10 V/m it either continues to perform its essential function or fails in a way that is safe and detectable. That pushes back into the design: how a corrupted sensor reading is caught, what the watchdog does, whether a reset mid-therapy is acceptable. Those are architecture decisions and they cannot be added at test time.
Can you help with software under IEC 62304?
We do firmware for the electronics we design and we work in a way that is compatible with 62304 — traceable requirements, documented reviews, controlled releases. Full 62304 compliance for a Class B or C item involves a lifecycle and a QMS that sits with you or a specialist partner. We will tell you which parts we can carry and which you need to place elsewhere.
Got a board to design — or one that won’t boot?
You talk to the engineer who would do the work. Reply within one business day, and we’ll sign your NDA before you go into detail.